To me, folk music is like folk art, it is from the "folk", meaning everyday people. Folk music has a purpose whether it is to make a statement "We Shall Overcome", "Carry it On", share beauty of the natural world, Bill Staines' songs come to mind, discuss loss of love, protest war, mourn slavery, stand up for civil rights, and so much more.
Folk music gets into our ears and into our souls. We hum it, we sing it, we remember the words. It is accessible to everyone, regardless of race, religion, or level of education.
I have played and sang folk music since I was 14 yrs. old. At 54, it still has a strong appeal. It doesn't grow old, though circumstances in which some of it were written may have changed.